Fluorescence based methods play an essential role in modern cell biology and biomedical research. Further development of these techniques has been hindered by the lack of suitable fluorescent probes. To overcome this challenge, various fluorescent nanoparticles have been developed. Among those, semiconducting polymer dots (Pdots) exhibit superior properties such as high brightness, fast emission rate, and excellent photo stability. Fluorescence based techniques encompass a broad area with a large market size, ranging from immuno-assays to super-resolution imaging. And while Pdot has proven to be an excellent general fluorescent probe, to maintain focus, to penetrate the market, and to generate adoption by the biomedical community, we have decided to go after flow cytometry applications, owing to its large market potential. During our 6-month Phase I SBIR project, we have developed Pdot450 and Pdot515 with ultra- high brightness, narrow-band emission, and high photo stability. To achieve this goal of penetrating the flow cytometry market, this Phase II SBIR project proposes to develop 5 additional Pdot probes to complement the 2 developed during Phase I. After this Phase II project, we will have completed a set of 7 Pdots so we may launch a Pdot series with high brightness and narrow emissions for flow cytometry applications. Furthermore, we will establish pre-production and quality control protocols for manufacturing this Pdot series.